. >>> the first debate between mitt romney and barack obama is one day away. both candidates are behind closed doors getting ready. the outcome of the debates could help decide the election. but both campaigns are downplaying expectation. cbs reporter tara mergener has more from the white house. >> reporter: workers are setting the stage for wednesday night's presidential debate at the university of denver. both candidates are behind closed doors today getting ready. mitt romney is preparing in colorado and the latest polls show he is trailing the president in most swing states. >> we can do this. >> reporter: his running mate paul ryan is on a bus tour working to sway voters in iowa. >> our goal is to earn your support. we want to deserve this victory. >> reporter: vice president joe biden is in the battleground state of north carolina today while president obama studies for the debate in nevada. he is holding practice sessions with former presidential candidate john kerry, playing the part of mitt romney. on monday, the president called campaign volunteers a